Automatic alarm switch



Patented Sept. 5, 1944 UNITED STATES PATENT OFFICE 1 Claim.

My invention relates to signal circuits of the automatic fire alarm type, and has among its objects and advantages the provision of an improved heat responsive switch which closes the alarm circuit when it is subjected to abnormally high temperatures.

In the accompanying drawing:

Figure 1 is a side view.

Figure 2 is an end view.

Figure 3 is a top plan view.

Figure 4 is an enlarged sectional view.

Figure 5 is a sectional View along the line 55 of Figure 4, and

Figure 6 is a sectional View along the line B6 of Figure 4.

In the embodiment of the invention selected for illustration, I make use of a support or frame I0 comprising a one-piece metal blank bent to provide spaced side walls [2 connected by an end wall l4. This frame may be mounted on a suitable support l6, as by bolts 18. The side walls l2 are bent to provide top and bottom walls 20 and 22, respectively, and overlapping end walls 24. A bolt 26 extends through aligned openings in the end walls to clamp the two together. This bolt serves as a connection for a circuit wire 28, which is electrically connected with the alarm (not shown). The frame It] also functions as a part of the electric circuit.

Diverging legs 30 depend from the side walls [2 and support a fixed shaft 32 upon which is mounted a heat responsive unit 34. This unit has an end 36 secured in a slot 38 in the shaft 32, and the unit is of spiral contour to distort when heated, in addition to constituting a conductor. The free end of the unit extends upwardly and loosely between the side walls I2, and spaced therefrom. A contact 40 is attached to the upper end of the unit 34.

Insulating blocks 42 and 44 are mounted on the side walls l2 to support a conductor strap 46, which is provided with a contact 48 engaged by the contact 40 when the unit 34 is flexed through heating to close the alarm circuit. A terminal strap 59 lies on the strap 46 and is clamped thereto by a bolt 52 anchored in the block 44. To provide adjustment for the strap 46 so that the point 48 may be spaced a proper distance from the contact 40, the strap is provided with a slot 54 for the bolt 52. The second wire 56 of the alarm circuit is attached to the strap 50. Both straps 4G and lie in a groove 58 in the block 44 to be restrained from rotation.

Two bolts 60 extend through the walls 20 and 22 and the block 44, which blocks are threaded into the block 44 to connect all these parts into a unitary structure.

Without further elaboration, the foregoing will so fully explain my invention, that others may, by applying current knowledge, readily adapt the same for use under various conditions of service.

I claim:

In a circuit alarm switch, an elongated rectangular frame of electric conductive material, a support of insulating material secured on the outer end portion of the frame, a conductor engaging terminal attached to the outer end wall of the frame, a second conductor engaging terminal mounted on the support, an L-shaped conducting member having its longer arm secured horizontally on the support in engagement with the terminal thereon, the shorter leg of the L-shaped member rising vertically, a contact fixed on the rear face of said shorter leg, a pair of Support legs formed integral with and depending from the opposite side of said frame, a shaft fixed to and extending transversely between said frame legs, a heat responsive element secured to and arranged spirally about said shaft, said heat responsive element having its outer end portion rising through the frame, and a second contact fixed to the upper end of said rising end portion in co-acting relation with the fixed contact so as to open and close the electric circuit through the conductors in accordance with the action of the heat responsive element.

CUTBERTO MEZA. 

